US President Donald Trump hailed the conservative activist Charlie Kirk as a great American hero and martyr during a speech to tens of thousands of mourners at a memorial service in Arizona.

Trump was the headline speaker at the packed event on Sunday, which saw top officials from his administration, including Vice-President JD Vance, praise Kirk's political legacy after he was shot dead on 10 September.

He was assassinated because he lived bravely, he lived boldly, and he argued brilliantly, Trump told the crowd at the State Farm Stadium near Phoenix.

Kirk's wife, Erika, also delivered a tearful speech in which she said she had forgiven her husband's alleged killer.

My husband, Charlie, he wanted to save young men, just like the one who took his life, she said, adding: I forgive him because it is what Christ did. The answer to hate is not hate.

Tens of thousands of people queued for hours outside the stadium before the event, with some even camping out the night before to secure their spot. Many wore Make America Great Again (MAGA) hats, other Trump-branded items, and red, white, and blue outfits.

Inside the stadium, the mood and atmosphere resembled a raucous political rally with music beforehand from Christian bands who prompted standing singalongs from the crowd of almost 100,000.

The list of speakers included members of Kirk's organisation, Turning Point USA, well-known figures in the conservative movement, Trump administration officials, and those who said they had been shaped by Kirk's work and right-wing Christian worldview.

They stressed the need to continue the 31-year-old's activism and emphasised his deep faith throughout the five-hour service. Kirk, shot while debating students at a university in Utah, was repeatedly described as a martyr.

Other speakers conveyed that his death would further revitalise the conservative movement in America, with Trump’s administration asserting its strength amidst political challenges.

Kirk’s activism focused on free speech and mobilizing the youth vote for Trump. His remarks on divisive issues often sparked backlash among liberals, making him a polarising figure.

The event highlighted the intensity of America’s political divisions, with Kirk's death being framed as emblematic of struggles between the left and the right.